Apparatus and method for locating an elongated workpiece within a multiturn induction heating coil



NOV. 12, 1968 p, N, SORENSEN 3,410,978

APPARATUS AND METHOD FOR LOCATING AN ELONGATED WORKPIECE WITHIN AMULTITURN INDUCTION HEATING COIL Filed OC. 22, 1955 ATTORNEYS UnitedStates Patent O APPARATUS AND METHOD FOR LOCATING AN ELONGATED WORKPIECEWITHIN A MULTI- TURN INDUCTION HEATING COIL Phillips N. Sorensen,Bedford, Ohio, assignor to Park- Ohio Industries, Inc., a corporation ofOhio Filed Oct. 22, 1965, Ser. No. 501,295 9 Claims. (Cl. 219-10.69)

ABSTRACT F THE DISCLOSURE There is provided a method and apparatus forpushing a billet yfrom an induction heating coil and for positioning asuccessive billet in the center of this coil. A pusher rod is providedwith a pole piece that can be selectively magnetized. This pole piecepushes the second billet into the coil and, then when magnetized, itpulls the successive lbillet back into the proper position within thecoil. When the successive billet is in the proper position, the polepiece is demagnetized and removed from the coil.

The present invention pertains to the art of induction hating and moreparticularly to an apparatus and method for locating an elongatedworkpiece within a multiturn induction heating coil.

The invention is particularly applicable for heating a ferromagneticbillet preparatory to forging the same and it will be described withparticular reference thereto; however, it will fbe appreciated that theinvention has somewhat broader applications and may be used for heatingvarious other elongated, -ferromagnetic workpieces.

In forging ferromagnetic billets into various intricate shapes, thebillet is first heated to the `forging temperature and, then, placedbetween the moving dies of a forge. At one time, these billets wereheated by placing them within a gas-red furnace; however, this heatingprocess proved to be relatively expensive 'because of the long timerequired for the workpiece to reach the forging temperature and, also,because of the high cost and extensive space required for the ygas-firedfurnace. Consequently, many of the forging installations have been, orare being, modified to use multiturn induction heating coils for heatingof the billets to the required `forging temperature. Heating the billetsby induction heating has proven to be a substantial advance in the art.

At first, the induction heating equipment for use in a forgingdepartment included a multiturn heating coil having an opening at oneend. The workpiece was placed through the opening into the coil, and itwas removed from the same opening after the workpiece was heated to thedesired forging temperature. Later, some induction heating equipment-for a forging department included a multiturn induction coil having apassageway therethrough with both an entrant end and an exit end. Afirst billet was placed into the coil and heated to the forgingtemperature. Thereafter, a second workpiece was placed into the coilfrom the entrant end. This ejected the previously heated workpiece fromthe exit end of the passageway.

Although this last mentioned type of induction heating equipmentsubstantially increased the productivity of the installation, there wasone serious limitation. The passageway of the induction heating coil hadan axial length substantially corresponding to the axial length of theworkpieces or billet. When the subsequent billet was forced into thecoil, it was moved to the exit end of the passageway to assure ejectionof the previously heated billet. Consequently, the workpiece was notcentered within the coil passageway. To the contrary, the billet wasadjacent the exit end of the coil. This prevented eflicient magneticcoupling between the coil and the billet, and somewhat reduced theover-all efficiency of the heating operation. In fact, sometimes therearwardmost end of the billet was not heated to the desiredtemperature.

The present invention is directed toward an induction heatinginstallation wherein a subsequent workpiece ejects a previously heatedworkpiece; however, in accordance with the present invention, thedifficulties heretofore eX- perienced when using this type of apparatusare completely overcome.

In accordance with the present invention, there is provided animprovement in the above-mentioned induction heating equipment. Thisimprovement includes the provision of a pole piece on the abutmentelement of the pusher mechanism which forces a subsequent workpiece intothe coil and, at the same time, ejects the previously heated workpiece.There is also provided a control means for selectively magnetizing andde-magnetizing the pole piece so that the unheated `ferromagneticworkpiece may be magnetically attracted to the abutment element andpositioned by the element within the coil after the unheated workpiecehas ejected a previously heated workpiece. Since the workpieces areheated above the Curie temperature 4for the purpose of forging, thepreviously heated workpiece is not magnetically attracted to themagnetized pole piece. This feature allows accurate positioning of theunheated workpiece Without affecting the ejection of the heatedworkpiece.

The primary object of the present invention is the provision of animprovement in an induction heating installation including a multiturncoil with a workpiece receiving passageway having an entrant end and anexit end and a pusher mechanism for yforcing an unheated Workpiece intothe passageway while simultaneously ejecting a heated workpiecetherefrom, which improvement allows proper placement of the Aunheatedworkpiece with respect to the coil.

Another object of the present invention is the provision of animprovement in an induction heating installation including a multiturncoil with a workpiece receiving passageway having an entrant end and anexit and pusher mechanism for `forcing an unheated workpiece into thepassageway while simultaneously ejecting a heated workpiece therefrom,which improvement includes a magnetic abutment element for the pushermechanism to hold the unheated workpiece while it is beingl positionedsubsequent to ejectment of the heated workpiece.

Still another object of the present invention is the provision of amethod `for locating an unheated, elongated workpiece within the centralpassageway of a multiturn induction heating coil after a heatedworkpiece has been ejected therefrom, which method is efficient inoperation and adapted for use by a slight modification of existingequipment.

These and other objects and advantages will become apparent from thefollowing description used to illustrate the preferred embodiment of theinvention as read in connection with the accompanying drawing in which:

FIGURE l is a side plan view illustrating, somewhat schematically, apreferred embodiment of the present invention;

FIGURE 2 is a partial side elevational view showing the ejectmentoperation of the present invention;

FIGURE 3 is a partial side elevational view showing the positioningoperation of the present invention; and,

FIGURE 4 is a cross-sectional view taken generally along line 4-4 ofFIGURE 2.

Referring now to the drawing wherein the showings are for the purpose`of illustrating a preferred embodiment of the invention only and notfor the purpose of limiting same, FIGURE 1 shows an induction heatingapparatus A for heating an unheated, elongated workpiece B and ejectinga heated, elongated workpiece C. Although the workpieces, when heated,may be used for various purposes, in accordance with the illustratedembodiment of the invention, the workpieces are billets to be forgedafter being ejected from apparatus A. Apparatus A comprises, asessential components, a coil assembly 1t) having a central, axiallyextending workpiece receiving passageway 12 with an entrant end 14 andan exit end 16, a pusher mechanism for sliding workpiece B into thepassageway 12, and a control device for controlling the pushermechanism, in a manner to be hereinafter described in detail.

Referring now more particularly to the coil assembly 10, this assemblyis a somewhat standard assembly in the induction heating art, and itincludes a multiturn induction coil 32 embedded within a casing 33 andhaving an internal coolant pasfage 34 connected with an inlet conduit 36and an outlet conduit 38, as best shown in FIGURES 2-4. The coil 32 isenergized by high frequency power supply, schematically represented as agenerator connected by lines 42, 44 with opposite terminal ends of thecoil. A switch 46 is utilized for selectively energizing the coil 32. Itis appreciated that this disclosure is only a schematic representation;therefore, various components such as power factor correcting capacitorsand controls for the generator have been eliminated for the purpose ofsimplicity. It should be appreciated that the power supply may deliverpower to the coil at various frequencies, i.e. line Afrequency to radiofrequency.

The coil assembly 10 includes a workpiece guide means taking the form ofspaced rails S0, 52 having a loadingr end 54 and an ejecting chute 56.The guide means for the workpiece as it passes into and out of thepassageway 12 may take a variety of other forms without departing fromthe intended spirit and scope of the present invention.

The pusher mechanism 20 includes an abutment element 60 connected ontothe outermost end of a rod 62. The rod is secured onto a piston 64slidably received within a fluid actuated cylinder 66. By introducinguid, such as oil or air on opposite sides of the pistons through controllines 70, 72, the piston 64 and, thus, abutment element 60 may be movedaxially with respect to the passageway 12 in a controlled manner, Tocontrol the movement of the abutment element, there is illustrated avalve mechanism 74 having electrical input lines 76, 78. The valvemechanism 74 is controlled by a known arrangement so that the piston 64moves in a controlled manner with respect to the passageway 12.

As so far described, apparatus A does not differ from previousmechanisms for loading and unloading coil assembly 10. A workpiece B isfed by an appropriate escapement arrangement onto the loading end 54 ofthe guide means, and the abutment element 66 forces the unheatedworkpiece B into the opening 12. This ejects the heated workpiece C. Asillustrated, the workpieces have a length L and the passageway 12 has alength L-l-Zx. Heretofore, the ejectment of the heated workpiece Cresulted in the workpiece B being positioned adjacent the exit end ofthe passageway 12. This can be seen in FIGURE 2. The spacing of theworkpiece B from the entrant end of the passageway 12 is (x-l-c) whilethe spacing of the workpiece B from the exit end of the passageway is(x-c). If the workpiece is heated in this position, the rearwardmost endof the workpiece is ineiciently coupled with the magnetic iield withinthe passageway 12, and uneven heating results. The present invention isdirected toward an arrangement for locating the workpiece B within thepassageway 12 so that an equal spacing x may be provided on each end ofthe workpiece. See FIGURE 3. In accordance with the invention, thepusher mechanism 20 includes a control device Sti. The abutment clement66 includes a ferromagnetic casing formed from a high permeabilitymetal, such as soft iron, and an internal spool S2 formed from a similarmetal. The spool is provided with axially spaced pole pieces 84, 86 andis surrounded by an electromagnetic coil 96 having input lines 92, 94,These lines are fed through an insulating tube 96 to an element 0f thecontrol device 30.

A cam 100 having a rearward shoulder 102 and a forward shoulder 104 issecured onto rod 62 so that movement of the rod actuates spaced switches110, 112 as the shoulders pass followers 114, 116 on these switches.Movement of the followers causes a signal which is conveyed throughlines 120, 122 to a relay box 130. The box includes relays, not shown,for connecting power leads 132, 134 onto the lines 92, 94 for energizingthe electromagnetic coil 90.

In operation, after the unheated workpiece B is positioned in front ofthe heated workpiece C, piston 64 is moved within cylinder 66. Thisforces the workpiece B into the position shown in FIGURE 2. This ejectsthe heated workpiece C down the ejecting chute 56. At this time, thefollower 116 contacts the shoulder 104 and energizes the electromagneticcoil 90. This magnetizes pole piece 86 so that the unheated workpiece Bis magnetically attracted to the pole piece. Thereafter, the piston 64starts movement away from the coil assembly 10. This pulls the workpieceB toward the entrant end 14 of passageway 12. When the workpiece iscentrally located within the passageway with the distance between boththe entrant end and exit end being x, the shoulder 102 of cam 100actuates follower 114 which, through relay box 130, disconnects powerleads 132, 134 from the lines 92, 94, This deenergizes theelectromagnetic coil and sub.tantially de-magnetizes the pole piece 86.Continued movement of the abutment 60 rearwardly by the piston 64 doesnot pull the workpiece B. Consequently, the workpiece remains centrallydisposed within the workpiece receiving passageway 12. After theworkpiece B is heated to the forging temperasture, the operation isrepeated to locate a subsequent workpiece within the passageway and heatthe same.

Even though the workpieces are formed from ferromagnetic material, theheated workpiece C is above the Curie point; therefore, it will not bemagnetically attracted by the pole piece 86. For this reason, the pole.piece may be magnetized as soon as the rod 62 starts its forwardmovement, or any time during the forward movement. In practice, thepo-le piece 86 is magnetized slightly before the start of the rearwardor retracting movement of the rod. This prevents control difficultiesand allows use of magnetic coil having lesser field strength. If thepole piece shifts from the unheated billet before the coil is energized,a considerable eld strength would be required to pull the workpiece Btoward the pole piece.

The present invention has been described in connection with a structuralembodiment; however, it should be appreciated that various changes maybe made in this embodiment without departing from the intended spiritand scope of the present invention as defined in the appended claims.

Having thus described my invention, I claim:

1. A method of heating a succession of elongated ferromagneticworkpieces in a multiturn induction heating coil having a centralworkpiece receiving passageway with an entrant end and an exit end, saidmethod comprising the following steps:

(a) sliding a rst workpiece axially into said passageway from saidentrant end;

(b) heating said first workpiece by said coil t-o a ternperature abovethe Curie point of said first workpiece;

(c) sliding a second workpiece axially into said passageway from saidentrant end until said rst workpiece is ejected from the exit end ofsaid passageway by said second workpiece;

(d) pulling said second workpiece toward said entrant end until thesecond workpiece is properly positioned in said passageway for optimumheating; and

(e) heating said second workpiece by said coil to a temperature abovethe Curie point of said second workpiece.

2. A method of heating a succession of elongated fer romagneticworkpieces in a multitum induction heating coil having a centralworkpiece receiving passageway with an entrant end and an exit end, saidmethod comprising the following steps:

(a) sliding a first workpiece axially into said passageway from saident-rant end;

(b) heating said first workpiece by said coil to a temperature above theCurie point of said Vfirst workpiece;

(c) sliding a second workpiece axially into said passageway from saidentrant end until said first workpiece is ejected from the exit end ofsaid passageway by said second workpiece;

(d) magnetically attracting said second workpiece to a movable member;

(e) pulling said movable member, and thus said second workpiece, towardsaid entrant end until the second workpiece is properly positioned insaid passageway for optimum heating;

(f) then releasing said second workpiece from said member; and,

(g) removing said member from said passageway.

3. A device for moving an elongated ferromagnetic workpiece axiallywithin the workpiece receiving passageway of a multiturn inductionheating coil, said device comprising: an abutment element, means formoving said element axially into and out of said passageway, a polepiece on said abutment and adapted to contact said workpiece, and meansfor selectively magnetizing said pole piece whereby said workpiece maybe magnetically attracted to said pole piece while said workpiece isbeing positioned within said passageway.

4. In an induction heating apparatus comprising a multiturn inductionheating coil with a central workpiece receiving passageway, guide meanswithin said passageway and coextensive therewith for supporting anelongated workpiece in said passageway, said coil passageway having anentrant and an exit end, and a workpiece pusher mechnism having aforwardmost abutment element movable in a first and second direction,said element pushing an unheated workpiece axially into said passagewaywhen moved in said first direction with the workpiece moving into saidpassageway causing a heated workpiece to be forced from said exit end ofsaid passageway before said abutment element is moved in said seconddirection, the improvement comprising: said abutment element including apole piece, control means for selectively magnetizing and demagnetizingsaid pole piece, said control means including a first device formagnetizing said pole piece at least before said element starts movementin said second direction whereby said unheated workpiece is attracted tosaid abutment element and a second device for demagnetizing said polepiece after said abutment element has pulled said unheated workpiece insaid second direction to the proper heating position within saidpassageway.

5'. The improvement as defined in claim 4 including an electromagnet formagnetizing said pole piece, said first device being a means forenergizing said electromagnet and said second device being a means fordeenergizing said electromagnet.

6. The improvement as defined in claim 5 wherein said devices are eachswitches for selectively connecting said electromagnet onto a powersupply.

7. The improvement as defined in claim 6 wherein said switches areoperated in response to the position of said abutment element withinsaid passageway.

8. The improvement as defined in claim 4 wherein said first devicemagnetizes said pole piece before movement of said abutment element insaid first direction stops.

9. The improvement as defined in claim 4 wherein said passageway has alength only slightly greater than the length of said unheated workpiece,and said proper heating position is generally a position with saidworkpiece centered in said passageway.

References Cited UNITED STATES PATENTS 2,457,758 12/1948 Vore 2l910.69 X2,556,234 6/1951 Strickland 2l9--10.69 2,604,577 7/1952 Strickland etal. Z119-40.69 3,051,811 8/1962 Koesling 2l9-l0.69 X 3,051,812 8/1962Gschwender 2l910.69

RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner.

